Fuse construction



Oct 16, 1951 s. I. LINDELI.

FUSE CONSTRUCTION Filed Jan. 2, 1947 5 Sheets-Sheet l E H. w

l Uyl/ENTOR. gard Ima/6% BY www Oct 16, 1951 s, 1. LINDELL FUSECONSTRUCTION I5 Sheets-Sheet 2 Filed Jan. 2, 1947 FEED ww my@ a W w,

[,lllllilllllll Oct. 16, 1951 s. l. LINDELL FUSE CONSTRUCTION '3ShetS-Sheet 5 Filed Jan. 2, 1947 www@ -l I INVENTOR ga/tz ZZUQeZZ, BY

Patented Oct. 16, 1951 UNITED STATES PATENT OFFICE FUSE CONSTRUCTIONSigurd I. Lindell, Chicago, Ill., assignor to S & C Electric Company, acorporation of Delaware Application January 2, 1947, Serial No. 719,849

(Cl. 20D-120) 12 Claims. 1

This invention relates, generally, to circuit interrupting devices andit has particular relation to fuses for use with alternating-currentelectric-power systems operating at high voltages, of the order of 115kv., where the transient recovery voltage may be substantially greaterthan the normal-frequency recovery-voltage, and where both large andsmall fault-currents may be encountered,

Fuses are extensively used in the primary connections to high voltagetransformers, and must be capable of clearing any fault current withinthe wide range of values obtainable in such service. For example, ashort circuit at the primary terminals will draw the full short-circuitcurrent that the generators and transmission equipment can deliver tothat point, which on a typical 115 kv. circuit may be as high as 6000amperes. A fault in the secondary circuit must draw its power throughthe impedance of the transformer and so will produce a much lowerprimary current but of low power factor. An extreme case is presented bya potential transformer. Such a transformer supplying only meters andrelays mal7 draw a primary current of a few milliamperes under normaloperation, and only a few amperes even when the secondary (output)terminals are short-circuited. In other installations, faults may beencountered that give rise to primary currents between these extremevalues. A fuse must be capable of promptly and surely interrupting anyvalue of current from the lowest that will sever its fusible element tothe maximum that the system can deliver on a short circuit.

In a fuse of the present type, wherein an arcing terminal is withdrawnthrough a bore of arcextinguishing material for extending the arc, thearc-passageway must be large enough to handle the largest possible faultcurrents without producing destructive pressures, but a small current,which the fuse must also be capable of interrupting, produces an arc ofsmall cross section which tends to be blown away from the walls of thepassagewair and so does not excite the production of sufficientarc-extinguishing gassuch as water vapor-from those walls for theeffective extinction of the arc.

In a fuse of this type it is desirable that the arcing terminalsubstantially fill the bore so as to minimize escape of exhaust gas pastthe retreating terminal, and also to give the terminal as high acurrent-carrying capacity as possible. The permissible closeness of thisfit must be determined by actual tests of the fuse and I have found thatunder certain severe operating conditions molten metal flows to the sideof the arcing terminal and solidies and thus reduces the clearancebetween the moving terminal and the bore. I have discovered thatcontributing causes of this difficulty are a tendency of the arc to findits root at the peripheral edge of the arcing terminal, and anunavoidable flow of some exhaust gas into the small clearance spacebetween the bore and moving terminal.

In accordance with the present invention a sealed reservoir is providedwhich contains a iiuid, such as carbon dioxide, that, when released intothe arc space, quickly fills it and provides a blast action which tendsto sweep out the products of the arc and to scavenge the inner surfaceof the arc passageway to remove therefrom material likely to form aconducting path thereover. The iiuid is released from the reservoirimmediately upon the rupture of the fusible, current-responsive element,and before the terminal in the arc passageway begins to movetheretthrough to extend the arc, so that even lowcurrent arcs aresubjected to a scavenging, arcextinguishing blast from their verybeginning'. The fluid is conducted through the moving terminal fordirect and efficient injection at that part of the bore that containsthe arc. Furthermore a blast of arc-extinguishing fluid is made to flowout of the space between the retreating terminal and the wall of thebore, and over the tip portion of that terminal to oppose the tendencyof the arc root to move toward the edge of the end-face of the terminal,and to oppose the flow of exhaust gases and molten metal into theclearance space.

Preferably, the carbon dioxide gas is stored under high pressure in areservoir attached to the movable terminal itself. The release of thisgas and the retraction of the movable arcing terminal are effected byspring mechanism all controlled by a single, fusible,current-responsive, restraining wire. The movable terminal may have ahollow bore through which this restraining wire may be threaded to reachthe control mechanism, and through which the gas may be conducted to thearcing tip for discharge into the arc space.

In accordance with the present invention provision is made forinitiating the functioning of the fuse in response to low currents suchas those produced in the primary circuit of a potential transformer onthe occurrence of a secondary fault. This, in combination with theprovision of the reservoir containing the arc extinguishing fluid whichis released into the arc passageway, provides a construction which willquickly and reliably interrupt the flow of fault current before anydamage can be done to the transformer and without nal-m to auiacentequipment, as might be the case 1I' the arc, once drawn by the iuse,were not promptly extinguished. Provision is made for carrying thecurrent carrying capacity of the fuse up to high values by employing, inaduit1cn to the strain wire, a fusible element having relatively largecurrent-carrying capacity.

Accordingly, these are among the objects of this invention: To provide alow-current, highvoltage fuse which shall be simple, ei'licient andaccurate in operation; to release an arc eX- tinguishing fluid from acontainer or reservoir to now into the arc passageway of the fuseimmediately upon the melting of the fusible element and beforelengthening the arc; to cause the arc-extinguishing fluid to flowthrough a tubular terminal, which is movable through the arc passagewayand which constitutes one of the terminals between which the arcincident to circuit interruption is drawn; to control the location ofthe arc root on the face of the moving terminal for preventing mobilematerial in the arc space from interfering with the movement of theterminal through the arc chamber; to envelop an arcing tip in a streamof gas flowing away from it; to restrain the operating mechanism of thefuse by a strain wire that extends through a tubular terminal; toprovide a spring operated mechanism restrained by a fusible,current-responsive element for releasing arcextinguishing gasimmediately upon Vthe rupture of that fusible element; to provideimproved means for releasing a store of arc-extinguishing gas early inthe operation of the fuse; and to provide an improved high-voltage fuseconstruction.

Other objects of this invention will in part be obvious and in partappear hereinafter.

This invention is disclosed in the embodiments thereof shown in theaccompanying drawings and it comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of thisinvention reference can be had to the following detailed descriptiontaken in connection with the accompanying drawings, in which:

Figures 1A, 1B and 1C, taken together, show a longitudinal, sectionalview through a fuse construction in which the present invention is'em-`bodied, the fuse being shown in the unblown condition, Figure 1B beingbroken near the midsection in order to show the details of constructionat the scale chosen within the limits of the space available;

Figure 2 is a detailed sectional View, at a larger scale, of the fuseconstruction as shown in the preceding figures at the section adjacentthe reservoir;

Figure 3 is a detailed view, at a larger scale, of the movable arcingtip in mid-operation;

Figures 4, 5 and 6 are sectional views taken along 'the lines -i, 5-5and '5-6 of Figure 3;

Figure '7 is a perspective View of the arcing tip shown in Figures 3 to6; and Y Figure 8 is a sectional view showing the present inventionadapted for higher current ratings through the use of a highconductivity fusible element, such as silver.

Referring now particularly to Figures 1A, 1B

and 1C of the drawings, it will be observed that the reference characterI3 designates an insulating tube which forms the housing of the fuse orcircuit interrupter to be described in detail hereinafter. At itsopposite ends the insulating tube H3 is provided with external or lineterminals H and l2 which are arranged to have contact engagement withsuitable terminal clips of a fusemounting (not shown) as is more fullyset forth in my copending application Serial No. 663,833, iiled April22, 1946, now Patent No. 2,484,839, issued AOctober 18, 1949.

As disclosed more fully in my copending application vSerial No. 663,834led April 22, 1946, the fuse herein disclosed is arranged to be mountedso that, when the fuse blows, it will automatically move or swing in itsfuse mounting, under the influence of gravity andthe biasing force ofthe contact clips, to a position in which an air gap is providedbetweeny the upper line terminal ll and the associated terminal clip.which is connected to the circuit. In order to provide such operationthe fuse has a latch tube i3 which is secured at its lower end to alatch release ange I4 that, together with the tube I3, is arranged to bemoved upwardly in a manner to be described hereinafter for the purposeof unlatching the locking mechanism on the fuse mounting and permittingthe fuse to fall or drop out to the open-circuit position.

At the central portion of the tube lil its internal diameter is smalleras indicated at I8 for the purpose of providing a section which hasgreater resistance to bursting pressure, because high pressures may begenerated within the tube i6 in the portion thereof in which `the arc isdrawn and extinguished. This configuration also aids in more uniformlydistributing the dielectric fluX in the air outside of the tube I@ aboutthe ends Vthe terminals embedded in the tube.

With a vView to providing an arcing passageway from whose surface anarc-extinguishing medium can be evolved, cakes .le of solid boric acid,or arc-extinguishing material are positioned along the bore of thesmall-diameter-section I8. These cakes i9 are annular in form and when.placed one above the other provide a continuousbore 2C! in which the arcmay be drawn and extinguished. At each end of the column of cakes if. ofsolid arc extinguishing. material there is provided a reenf'orcing ringof .suitable-insulating material, such aslber. One of these isfindicatedat 2s-:at the -upper end inFigure 1B and the other is indicated at 25`at the lower end. The reenforcing ring 25 is flared outwardly tofacilitate the outward ow of the products of the arc, yas will bereadily understood.

Moi/ably mounted within the bore 26k in the cakes .i9 of solid? arcextinguishing material is a hollow, rodlike, or tubular terminal v255,.which is mol/cable through. the bore Z byl mechanism that willv bedescribed in detail hereinafter. At its upper end the terminal 25J Yhasa contact tip N threaded onto it. As is shown` more clearly in Figure 2,the Contact tip 2'! hasfa cylindrical contact portion 28 making contactwith the inturned ends of contact fingers 23 that are biased inwardly bya garter spring 3Q. The contact fingers 29 are formed by longitudinallyslotting a tubular shell 3l. The base section of the shell 3| mayberolled into a fia-nge 32 which extends upwardly from a Contact fitting33, theA lower -end of which is shaped to conform to the adjacentsurface-of the-fuse tube I6 and bears against the reenforcing ring- 24andfservesto holdit in place,

The contact fingers 29 by their engagement with the contact tip 21 serveto provide a low-resistance, high-current-carrying, separable connectionbetween the fitting 33 and the contact tip 21.

As is shown best in Figures 1A and 1B, an electric connection betweenthe line terminal II and the contact fingers 29 is provided by aconducting tube, or terminal extension, 34 of brass or conductingmaterial. It will be noted that the lower end of the conducting tube 34is threaded onto the contact fitting 33 and that a nut 35 is threadedonto the upper end of the tube 34 and also is threaded into the lineterminal I I, thereby forming an extension thereof. A lock nut 36 servesto hold the contact nut 35 in place.

As will hereinafter appear, it is desirable that, when the fuse blows,the tubular terminal 26 be withdrawn through the bore 26 in order toextend the arc therein and permit the heat thereof to evolvearc-extinguishing water vapor from the cakes I9 so as to deionize thearc space and assist in extinguishing the are. In order to move thetubular terminal 26, a helical compression spring 31 lies within theconductor tube 34 and at one end bears against the tting 33 and at theother end against the underside of a spring seat 38 which is secured tothe lower end of a brass compression tube 39. The compression tube 39.The compression Atube 39 carries a base 49 at its upper end from which astud 42 depends. On opposite sides of the lower end of the stud 42,straps 43 (only one of which is shown) are pivoted by a pin 44. Betweenthe straps 43 a pulley 45 is rotatably mounted on a pin or shaft 46.

A cable assembly, shown generally at 41, extends over the pulley 45 andprovides both mechanical and electric connection to the tubular terminal26 for effecting reaction thereof and for maintaining electric circuitconnection thereto while it is being move-d through the bore after thecontact tip 21 has moved away from the contact fingers 29. The cableassembly 41 consists of a core 48 formed of a large number of strands offine copper wire, and an outer sheath 49 formed by a closely wound coilspring of stainless steel. One end of the cable assembly 41 is connectedby a strap or cable link 5I) to the terminal fitting 33.

The other end of the cable assembly 41 has a threaded terminal 52 whichis screwed into a connecting tube terminal 52. This terminal carries abushing 53 which in turn carries a flask holder 54 at the lower end ofwhich is fastened a sleeve 55 for carrying the contact 5 tip 21 and thetubular terminal 26. Slideable within sleeve 55 is a needle holder 56having cylindrical guide portion 51 and a central rod portion 58connected by a perforated web 58. This needle holder 56 is urgedupwardly in the sleeve 55 by a coil spring 66 and it carries a needle 63for puncturing the diaphragm 65 of a ask 66 mounted in the holder 54.This flask or reservoir 66 is a steel capsule filled with carbondioxide. Such capsules are well known and readily obtainable on themarket. The needle 63 has a notch 64 at such a distance from its tipthat when the top of the cylindrical guide portion 51 of the needleholder abuts against the shoulder 6I of the ask holder 54, the notch 64lies in the hole of the diaphragm 65 and so permits the escape of thecarbon dioxide. The gas so released, flows down through the tube 55,passing through the perforated web 56 and the needle holder 56, andthence down through the tubular terminal 26.

Normally the needle holder is held in its lowermost position by a strainwire 59, the upper end of which is fastened in the lower end of thecylindrical portion 58 of the needle holder 56. This strain wire extendsdown through the terminal 26 and forms a part of the current responsivemeans employed for effecting operation of'the fuse as will be describedin detail hereinafter. As long as strain wire 59 remains taut it holdsneedle holder 56 in its lowermost position within the sleeve against theforce of spring 60 and also holds the sleeve 55, and with its terminal26, in the lowermost position against the force of spring 31. Whenstrain wire 59 slackens, it releases the needle holder 56 for operationwithin the sleeve 55 and thereby releases also the Whole mechanism forwithdrawing the tubular terminal 26 upward through the bore 20 in thearc extinguishing material I9.

The force exerted by spring is nearly equal to that exerted by spring31, and the inertia of the needle holder 56 is very small compared tothat of the tube 54, pulley 45, cable 41, sleeve 55, terminal 26, andother parts moved by spring 31. Consequently the needle holder 56experiences a much higher acceleration than does the terminal 26 and sotravels the inch or so required for puncturing the capsule 66 during thetime that the terminal 26 moves a much smaller distance. Thus the arcextinguishing gas is released from the capsule 66 by the time thetubular terminal 26 has moved a small fraction of an inch, and impelledthrough the bore of the terminal 26 by the high pressure, reaches thearc space promptly thereafter. The full stroke of terminal 26 is about24 inches in a 115 kv. fuse and is completed in about one-tenth second.

At the lower end of the tubular terminal 26, an arcing tip 1I is carriedas is best shown in Figures 3 to 7 inclusive. This tip is ofsubstantially solid metal and is uted at 12 to conduct the arcextinguishing gas into the space between f the tip 1I and the surface ofthe bore 20 in the boric acid cakes I9. As may be seen in the sectionalviews of Figures 5 and 6, the flutes 12 are large compared to thecentral bore 16 through which the strain wire extends so that the flutes12 offer the freest path for the gas. While the tube 26 nearly lls thebore 20 so as to impede the upward escape of gas from the arc space, tip1I is smaller in diameter so as to leave sufficient clearance for thefree flow of the gas from the flutes 12. The gas from the tube 25 thussweeps downward over the surface of the tip 1I as indicated by arrows inFigure 4 for controlling the arc. These gases also sweep over thesurface of the bore 20 at the receding end of the tubular terminal 26and of the arcing tip 1I, thereby directly sweeping out particles ofconducting matter or the like which may facilitate the restriking of thearc once it has been extinguished.

As shown more clearly in Figure 1B, the strain Wire 59 has a reducedsection 13 adjacent the lower end of the arcing tip 1I. The purpose ofthis is to provide a portion of the strain wire 59 which will melt inpreference to other parts of this Wire on the occurrence of relativelyheavy fault current. It will be apparent that when the section 13 melts,the resulting arc will be formed near the end of the arcing tip 1I sothat full use can be made of the bore 20 for drawing the arc therein toaid in extinguishing it.

'I'he lower end of the strain wire 59 is secured in;a .tubular terminal4extensionf'IlI cfa terminal 15. The extension 'Ill is deormeclionto the`end ofA the strain wire. 59. `for providing, mechanical and electric.connections .to it.

Asindicated hereinbefcre, :itizmaybe desirable to employ thefusefconstructioncoithe..present invention toVp-rotecting potentialtransformers. The mormal current .flow .to .the'apotential transformeris.. relativelyfsmall, and under` certain conditions, .the `iiow .ofauItcurrent .thereto maxT also besmall :but yet of suicientxamennttorequire that the circuit be interrupted. Thus, it is .necessary :toprovide anurrent .responsive element V-which is 'capable oi"A releasingthe strain wiref59 at a relatively.smallnverload .fbut which still hassufficient mechanical strengthto withstandthe Aforceof .springs ill and6!) :and .restrain their. movement. f For this Fpurpose a .fuse .linkconstruction,.indicated generally .at 16,.:may .rbe employed, theconstruction .of which .isset forth in detail in Lindell PatentNo.12,0.84 ,495. The fuse link assembly "i6 .includes a terminal v'II.which may be .threaded Vinto .the Aterminal T5. -Oneuendof `aconducting link 'i8 is pivoted to the terminal 'I1 and the other .endhas an .eye that receives a lever 'I9 vwhich isthe .first Aof a set V.ofinter-related levers :comprising :additional levers .Bil and 8l. The.levers 51.9,. 80 `and :8l `are fulcrumedbetween p1ate`s82 (only one oiwhich is shown) of insulating material that, in turn, .are supported on.a terminal 83. A fusible element 84 in .the form ofar-relatively'iine'wire mechant- `cally and velectrically :connects thevlever SI vwith .the terminal 83. The .size of the wireffi .determinesain v:part the time-current .characteristics of the fuse y'link assemblyi6.` #Because .of lthe mechanicalradvantage vprovided 'by-the =leversf19, Btl-and 8'I the full force of the lspring 3-7 is not applieddirectlytto'ithe fuse wire 84.- Accordingly, it. can .be calibrated itomelton -low lof a predetermined low .current lwith :an accuracy thatwouldbe impossible -if the wire84 'were required to withstand the fullforceof lthe spr-ings'ifl `and 56D.

The fuse .linkfassembly TIS A.is .particularly iintended tooperate when:the .ow of-fault current isrelatively .low and .persists .over :anextended period. VInzsuch case, :the Ifuse wire 281i will nallypartzandrelease the levers 19,186 andLSL-.where- .upon fthe springs e6I!.and 31 .act immediately, bas described hereinbefore, topuncture theA.dia- :phragm Y'65 vand release ithe. .arcextingu'ishing fluid .from`:the reservoiror flask l66 into :the tubu lar :terminali .25.:Inuthiscase the. arc `will fbe zdrawn tbetween the receding Aend oi the:link .im and. the lterminal .83 Terminal-smem'bers P5 and 71 andlinkffl are smallenoughltoenter .the bore 120 for extending the arcAthereinifto. be extinguished. The arcwill Vbe of relativelysmall cur.-Y'rent .magnitude and :thearc :extinguishing uid -fromithe reservoir.onaskii Vwill materially assist-in extinguishing it ysince itl1e..arcis 'unlikely to-evolve 'the necessary amount ofarc YextinguishingVmedium from lthercakesfl' of larc @extinguishing material. Thescarbon.dioxide blast persists-after the lextinctionof the Y.arc and so* asweeps vout. all residual :ionizedYl-and conducting vparticles from Ythe space between-'the .arcing .terminals, and increases the rateatwhich lthe :arc- `space builds up its resistance torany' tendency of thearc to restrike inv response to the -recovery voltage that appearsratthe fuse terminals promptly after the-arc interruption AWhen arelatively Vheavy 'fault current Vflows, `as in the case of ashortcircuit, both .the Areduced section 113 oi the strain Vwire 59,and-the A663,833. :the fitting I08,.in part,.bya sleeve IDS over whichfuse wire .84 will melt immediately. VThe func-I tion-ingof theV springs.Bland 6B in withdrawing the Vtubularrterminal 2.6 and Areleasing the,-arc extinguishing uid -from 'the` reservoir .or flask I Swillibe.thesameas-.already described. The terminal 1.1, being thus.leftunsupportedusimply fallsY harmlessly into zthe exhaust passage. Thearc promptly establishes itself between terminal f8.3A and tip "H oftheretractable terminal 2t.

Asin .the caseof the low-current fault, the arc rextinguishinggasissuing .from the tip 'II assists 'in the creation-of a blast downthrough the bore '26, although-inthis case the arc isflarge enough:that'it also releases large amounts of water vapor fromthe boricracidI9. The force of the carbon dioxide gasfrom the iutes "I2 opposes anymigration of the arc root toward the edge i9 and Aalso any flow of metalto thisV edge. Thusthe gas issuing fromthe'tub'e 25 insures that thearcwill not enlarge the :tip II to impede the free movement of theterminal in the bore 2E?. This Acon- :trol ofthe arc permits smallerclearance to be lemployed.

.As inthe casev vof the 'low current vfault, the carbon dioxide blast,bili-persisting after the extinction of thearc vvand sweeping outresidual conducting particles, increases theirate Vat which the arcspace builds up Aits resistance to 'restriking The terminal S3isconnectedto the lower fuse tube terminal I2 by a rod `85; The lower.end of the rod 85, as viewed in Figure `1C,is secured ito a narrowbridge that is carried by a metalexhaust tube 8l. The `metal exhausttube Si 'exn tends well'up into the lower end ofthe fuse tube Il) forassisting in more uniiormly'distributing the electrostatic stressincident to circuit interruption, as is set forth .in more completedetail iin the .copending application of Lindell and Baker,

Serial No. r663832,'1ed April 22,v 1946. A nut isithreadedonto thelowerl end of the tube 81 and `is also 'threaded into Ythe ylower fusetube ter- -minal l2 Ito provide connection thereto. A lock nut 89 -holdsthe nut 88 in place.

The fuse is arranged to expel lthe gases from thearc down through thelower line terminal I2. In order to -cool and condense thearcproductszandlimit the escapeof ame from the lower end of-the fuse, a .condenserassembly of the type shown in Triplett Patent No. 2,379,200 `may be.provided Within theshell I6 just below the -terminal I2.

It will be recalled that the fuse construction .disclosed herein lcan-be employed ,as part of a drop-out fuseconstruction as shown .in my cof:pendingapplication Serial No. 663,834. It is for this purpose Vthat thelatch tube I3 (Figure 1A) is provided. When the fuse blows and thecompression tube 39 is driven upward by the spring 43.7, it carries withit the base 4i! until the latter engages .a cap 164 thatiis ,secured tothe upper end of the Alatch tube i3. Thereupon, the latch Vtube I3 `ismoved upwardly to lift therewith the flange I4 which releases the -latchin the fuse mounting (not shown) to permit the fuse to drop out. Thelatch tube I3 moves upward until a flange |05 `shown in Figure 1B, onthe spring seat 38 engages a shoulder IBS, Figure 1A, on .the inside ofa stop tube I'l that is secured `to a fitting 108 which forms a part ofthe fuse mounting contact mechanism that is described in more detail inmy copending rapplication Serial No. The stop tube. I'l is held in placein the lower end ofthe tube `I 01 .is .rolled and which bears .againstthe v.underside of the /tting l.

The latch tube I3 is held in the position shown in Figure 1A of thedrawings by a coil compression spring I I0 which is located between thetubes I3 and I 01 and at its lower end bears against the upper end of atubular extension III from the flange I4 and at its upper end againstthe underside of a collar IIZ which is secured to the upper end of thestop tube Ill. The tting HIS has integrally formed ears I I3 and I I4 onopposite sides between which links are pivoted to provide for contactengagement between the line terminal i I and the cooperating fuse clip.

As illustrated in Figure 8, it may be desirable to omit the low-currentfuse-link assembly 16, shown in Figure 1B, and connect the strain wire59 having the reduced section 'I3 therein to provide a preferred blowingsection, directly to a connector II8 that may be supported by a narrowbridge IIS secured mechanically and electrically to the exhaust tube 81.

Where a still higher current rating is required, a fusible element |20,in the form of a coil of silver wire also can be used. As shown inFigure 8, the coiled fusible element I'2D serves to interconnect thearcing terminal II and the connector IIB, the same being deformed ontothe ends of the fusible element I20.

Since certain further changes can be made in the foregoing constructionsand different embodiments can be made without departing from the spiritand scope thereof, it is intended that all matter shown in theaccompanying drawings and described hereinbefore shall be interpreted asillustrative and not in a limiting sense.

What is claimed as new is:

1. In combination in a circuit interrupting apparatus having a body ofarc extinguishing material in which there is a longitudinally extendingbore, a pair of terminals between which an arc may be drawn one of whichis tubular and rea tractable through said bore for enlarging the arcspace between them, a chamber iixed to the end of said tubular terminalaway from the arcing end, a capsule containing an arc extinguishingmaterial ixed in said chamber, a cutter reciprocable in said chamber,spring means Within said chamber for actuating the cutter to puncturethe capsule, separate spring means for retracting said tubular terminal,and fusible tension means extending through said tubular terminal andholding both said cutter and said terminal for restraining theiroperation by said spring means.

2. In combination in a circuit interrupting apparatus, a body of arcconning insulating material having a bore, a pair of arcing terminalsone of which is movable through said bore away from the other terminal,means forming an arcing tip on the movable terminal, said tip beingsufliciently smaller in cross sectional area than said movable terminaland said bore as to permit free iloW of gas therepast, a portion of saidmovable terminal having a close fit in said bore for impeding the ilowof gas therepast through said bore, a reservoir for holding materialwhich when released is in the form of an arc extinguishing iluid, meansfor retracting said movable terminal through said bore away from theother terminal for enlarging the arcing space between them, releasablemeans holding said movable terminal against retraction, said movableterminal having duct means for conducting said arc extinguishing fluidfrom said reservoir into said bore at a position between said arcing tipand said portion which has a close nt with the bore, and

10 discharge means operable during the initial movement of said oneterminal for releasing said material from the reservoir, whereby itilows into said bore, envelops said arcing tip and enters said arcspace.

3. In combination in a circuit interrupting apparatus, a body of arcconfining insulating material having a bore, a pair of terminals, one ofwhich is hollow and movable through said bore away from the otherterminal, releasable means holding said hollow terminal againstmovement, and arcing tip on said movable terminal which is suiiicientlysmall than said movable terminal and said bore to permit free iiow ofgas between said arcing tip and the wall of said bore, a reservoir ofarc extinguishing material at the end of said tubular terminal away fromthe other terminal and movable with said tubular terminal, and dischargemeans operable from the beginning of the retraction of said movableterminal for releasing the arc extinguishing material from saidreservoir and conducting it through said tubular terminal, said tubularterminal and tip having a duct for conducting said arc extinguishingfluid from said tubular terminal into that part of said bore immediatelysurrounding said arcing tip.

4. In circuit interrupting apparatus having a body of arc extinguishingmaterial in which there is a longitudinally extending bore, and a pairof relatively movable terminal members between which an arc may bedrawn, one of said terminals being tubular and biased for movementthrough said bore, in combination, a reservoir movable with said oneterminal for holding material which when released is in the form of anarc extinguishing iiuid, discharge means cooperable with said reservoirfor releasing said iluid therefrom to ilow through said tubular terminalto assist in extinguishing said arc, a spring biasing said dischargemeans toward releasing position, and current responsive meansrestraining said tubular member from movement through said bore and saiddischarge means from movement by said spring until a predeterminedcurrent flow takes place whereupon said discharge means is operated torelease said uid to llow through said tubular terminalat about the sametime that it starts to move through said bore.

5. In circuit interrupting apparatus having a body or" arc extinguishingmaterial in which there is a longitudinally extending bore, and a pairof relatively movable terminal members between which an arc may bedrawn, one of said terminals being tubular and biased for movementthrough said bore, in combination, a reservoir movable with said oneterminal for holding material which when released is in the form of anarc extinguishing uid, discharge means cooperable with said reservoirfor releasing said fluid therefrom to iiow through said tubular terminalto assist in extinguishing said arc, a spring biasing said dischargemeans toward releasing position, and a tension element arranged to bereleased on flow of predetermined current through said terminal membersrestraining said tubular member from movement through said bore and saiddischarge means from movement by said spring until said predeterminedcurrent ilow takes place whereupon said discharge means is operated torelease said iluid to flow through said tubular terminal at about thesame time that it starts to move through said bore.

6. In combinaion in a circuit interrupting apparatus having a body ofarc extinguishing materia-l inA which there is `a longitudinallyextending` bore, apair Vof. terminals between whichfan arci may be drawnone of which'V is tubularuand retractable through: said bore :forenlarging the arc space between them, a reservoir `for holding amaterial which when released isyin theform of an arc' extinguishingfluid, sai-d reservoir being movable withsaid tubularterminal andconnected theretol for directing said material through said terminalinto said arc space, an ,opener movable relative to said tubularterminal and reservoir for releasing said material there- :from'and'.operatively connected to said tubular terminal'te preventretraction thereof, and a severable tension element connected to saidopener for holding it at the limit of its. motion relativeto saidreservoir in the non-openingposition, and for lthereby holdingsaidtubular term-inalv against. retraction.

'7. n combination in a circuit interrupting apparatus, a body of arcextinguishing material having an arc passage therein, meansfor ydrawingan varc in said passage including a stationary terminal. and a tubularterminal retractable therefrom through :said passageway, a pair ofmembers comprising a reservoir for holding a material which whenreleased is inthe form' of .an arc extinguishing ilui'd andan opener forsaid reservoir having. limited movement relativev to said reservoir.;one' ofV said membersfbeing movable with said tubular terminal Vand theother being movable relative thereto and operatively connected theretotoprevent'retraction thereof, and a fusible tension element connectedfrom. the

other member', and extending through'said tubular vterminal to thestationary terminalfor holding said other Vmember at a noneopenin-gposition in itsmotionrelative to saidY one member and for therebyholding said tubular terminal. `against retraction.

8. In combination in a circuit interrupting apparatus havinga body ofarc extinguishing material. in which there is a longitudinally extend.-ing bore, a pair of Vterminals between which an are maybe drawn one. ofwhich is tubular and retractable throughy :said bore for enlarging thearc space between them, a chamber carried by said! tubular terminal atthe end away from. the arcing end, av capsule' containing an arcextinguishing material in said chamber, a cutter'recipro'cablel in saidchamber for opening the capsule and operatively connected to saidchamber therebytol prevent retraction of said tubular terminal, a-severabl'e tension element connected Vto. said cutter at one end forholding .it way from said capsule, said tension element extendingthrough said tubular terminal and connected at itsl vother end to theother terminal, said tension element on being severed allowing saidcutter to open said capsule and thereby its contents to` flow throughsaid tubular terminal` into said bore while the former is retractedthrough the latter.

9. The combination of the immediately preceding claim Wherein'saidcapsule lies at the end of said chamber remote from the arcing tip ofsaid tubular terminal and said tension element holds said cutter in itsextreme position toward said tubular terminal.

10. In combination in a circuit interrupting apparatus having a body ofarc extinguishing material in which there is a longitudinally extendingbore, a pair of terminals between which an arc may be drawn one of whichis tubular and i2 retractable through- 'said-i bore .for enlarging. thearc space between them, a reservoir forholding material which whenreleased is in the form of an arc extinguishing fluid, said reservoirbeing located at and xed. to the end of said tubular terminal away fromthe arcing end and .arranged to discharge said fluid therethrough, anopener for said reservoir having limited movement Vrela'- tive theretoand operatively connected to said tubular terminal to prevent retractionthereof, spring means for operating said opener to release the materialfrom said reservoir, separate vspringy means for Vretracting. said'tubular terminal, and a singlek severable tensionelement'interconnectingsaid opener and theotherY of said pair of terminals Vand restrainingboth of said .spring means.

.11. `In combination in a circuit interrupter havingV a body of 'arcextinguishing material in which there is a longitudinally extendingbore, apair of arcing terminals, one ofwhich is tubular and movablethrough said bore, driving means acting on saidtubul'ar terminal forseparating itV from the other terminal and forming an arc spacetherebetween, a fusible tension element extending through said tubularterminal and providing a connection between the other terminal and' saiddriving means for restraining said'A driving means, means constituting asource of fluid arev extinguishing medium incommunication with theopening through said tubular terminal at a point remote from its arcingend at least during a portion of its movement through said bore, andmeans for releasing said fluid arc extinguishing medium to flow throughsaid opening following rupture -oi said fusible tension element.

12. In circuit interrupting apparatus, in combination, a body of arcextinguishing material having a bore, a pair of relatively movableterminal members Ybetween which an arc may -be formed, one of saidterminal members being located adjacent one end of said bore and theother being'tubular in character and movable through said bore, areservoir movable with said tubular terminal for holding material whichwhen released is in the form of an arc extinguishing iluid, mechanismfor moving said tubular terminal member, puncturing means carried by andmovable relative to said tubular terminal for releasing said fluid, andmeans for operating said puncturing means to release said uid to ilowthrough said tubular terminal member into said bore and the arc spaceduring the initial movement of said mechanism for assisting inextinguishing the arc before and while the same is withdrawn into saidbore and for blowing out of said bore products of the arc deposited on'the surface thereof and likely to facilitate restriking.

` SIGURD I. LINDELL.

REFERENCES' CETED Thewfollowing references are of recordk in the le. ofthis patent:

UNITED STATES PATENTS Number Name Date 2,319,276 Triplett May 18, 19432,319,277 Triplett May 18,. 1943 2,328,825 McMahon Sept. '7, 19432,343,422 Rawlins Mar. 7, 1944 2,353,528 Triplett July 11, 19442,491,956 Curry Dec. 20,1949

